The application manager on Omega2 dash tells you that Node-Red can't be installed on this device.
Nevertheless I was able to install it.
extend memory according to: https://docs.onion.io/omega2-docs/boot-from-external-storage.html
please consider that some lines of the documentation are outdated. For example: ummount /tmp/mounts/SD-P1 has to be replaced by umount /mnt/mmcblk0p1
opkg install node
opkg install oos-app-nodered